Indicating devices of the type, including a rotatable indicating implement



March 27, 1956 BOOTH 2,739,481

(3. H INDICATING DEVICES OF THE TYPE, INCL. ING A ROTATABLE INDICATI Filed May 2,

IMPLEMEN 50 fbrlisfqoher #049600 50;: 7%

United States Patent INDICATING DEVICES 9F THE TYPE, INCLUDING A RQTATABLE EJDICATING IMPLEMENT Christopher Hodgson Booth, Shefield, England, assignor to Firth-Brown Tools Limited, Sheffieid, England, a British company Application May 2, 1954), Serial No. 159,603 Claims priority, application Great Britain May 5, 1949 9 Claims. (Cl. 73-411) The invention relates to indicating devices (e. g. pressure gauges, dial test indicators and temperature indicators or controllers) of the type embodying a rotatable pointer, dial or other rotatable indicating element.

It is an object of the invention to provide in devices of the above type improved actuating means for the indicating element and more particularly actuating means which are of simple construction, low inertia and, in the preferred form of the invention, shock-resisting.

The invention consists in an indicating device of the above type embodying actuating mechanism for the indicating element comprising, in combination, a spindle which is supported for rotation, which carries the indicating element or is operatively connected thereto (e. g. by gearing) and which is provided with a steep-angled helical groove or rib, the edges or sides of such groove or rib thus constituting steep-angled helical abutments, and a blade which has one end engaging within the helical groove or with the rib, with the width of the blade substantially parallel to the groove or rib at the position of engagement and which blade end is movable in a direction substantially perpendicular to the edge of the groove or to the rib at the aforesaid position in response to changes in the pressure, temperature or other characteristic to be indicated whereby changes in the characteristic are translated into rotational movement of the spindle by engagement of the blade with an edge of the groove or of the rib.

In one form of indicating device the blade is resilient and is biased to rotate the spindle in one direction and there is a stop movable in response to changes in the characteristic to be indicated to limit the movements of the blade in the direction of its bias in accordance with the value of the characteristic at any time. Preferably the stop engages the blade intermediate in its length so that the resilience of the blade tends to reduce the transmission to the spindle of shocks derived from movements of the stop.

In the usual construction of the form of the invention just described the resilient blade will be biased to rotate the spindle to move the indicating element to the position of full-scale deflection and the stop will be arranged to limit the movement in this direction in accordance with the value at any time of the characteristic to be indicated.

There may be secured to the main blade for movement therewith a second resilient blade (herein referred to as the anti-backlash blade) which, in the case where the main blade engages in a groove in the spindle, also engages in the groove and is biased away from the main blade so that the two blades engage the opposite edges of the groove under resilient pressure thereby to prevent backlash. In the case in which the main blade engages a rib on the spindle then the two blades are biased towards one another to grip the rib between them. When the main blade is biased to rotate the spindle as aforesaid the anti-backlash blade is preferably of substantially Weaker spring material so as to exert less pressure on the spindle than does the main blade.

2,739,481 Patented Mar. 27, 1956 A specific construction of pressure gauge according to the invention and some modifications thereof will now be described by way of example of the invention and with reference to the accompanying drawings in which:

Figure 1 is a front view of the gauge with the dial broken away to show the operating mechanism,

Figure 2 is a sectional view in the direction II-II in Figure 1,

Figure 3 is a part view in the direction IlI-III in Figure 1.

Figure 4 is a View showing the engagement of the blades with the spindle,

Figure 5 is a detail view showing the means for attachment of the stop pin,

Figure 6 is a view corresponding to Figure 4 and showing a modified arrangement,

Figure 7 is a view showing a modified form of spindle and supporting bearing, and

Figure 8 is an enlarged view of the arrangement at one end of the spindle shown in Figure 7.

In the pressure gauge shown in Figures 1 to 5 the spindle is provided with a central parallel portion it reduced at each end to short pivots 2 and 3 supported in jewel bearings 4, 5 in the frame 6 of the instrument. Spring pads (not shown) engage pointed ends to the pivots to resist axial movement of the spindle. The pointer 7 is secured to the parallel portion of the spindle at one end thereof and is cranked in the manner commonly employed in electrical instlurnents such as voltmeters to pass through a central hole in a calibrated dial and to lie adjacent to the face of the dial. The pointer, which is of light construction balanced by weights 9, is arranged to move through 300 to 350 over the dial.

The parallel portion 1 of the spindle is formed with a helical groove lltl extending from the pointer to the opposite end of this portion of the spindle. The helical angle of the groove is about 30 to 45 to the axis of the spindle and the groove has about one complete turn on the spindle.

Secured by one end to the instrument frame 6 there is a fiat spring blade 12the main blade-of which the other end is received within the helcal groove 18 of the spindle and so makes a tongue and groove connection with the spindle. The width of the blade, which is substantial, lies at the helix angle (see especially Figure 2) and the length of the blade extends radially from the spindle. The blade is biasedto the left as viewed in Figures 1 and 4-to rotate the spindle by engagement with the edge 15 of the groove to move the pointer clockwise as viewed in Figure l to the full scale deflection.

Attached to'the'rear face (considered in the direction of bias) of the main blade for movement therewith there is a short anti-backlash blade 20 biased to engage with light pressure the opposite edge 23. of the groove, the pressure being sufficient to ensure that movement of the main blade in either direction causes rotation of the spindle without backlash. The width of the two blades is substantially the same. The main blade has a thickness of about .005 inch and the anti-bael lash blade a thickness of about .003 inch.

The guage is provided with a pressure responsive Bourdon tube 25 of strip form as described in my U. 8. Letters Patent No. 2,712,240, July 5, 1955. The free end of the tube is provided with a pointed screw 26 which constitutes the above-mentioned stop and engages the front face of the main blade 12 intermediate (perferably centrally) in the length of the blade and, at zero pressure, exerts a force on the blade suficient to deflect the blade, and with it the pointer, to bring the pointer to the zero position of the dial. The screw is adjustable in a nut 27 carried on the end of the tube 25 to vary the force on the blade and the nut may be swivelled in its supporting bracket 28 to vary the position at which the screw engages the blade and hence the leverage exerted on the blade. Application of internal pressure to the Bourdon tube causes the screw to move to allow the blade to follow-up in the direction and by an amount, appropriate to move the pointer to the dial indication corresponding to the applied pressure.

In the operation of the guage the strip moves against the edge of the groove with little sliding action and there is accordingly little frictional resistance to the movement. The guage has a minimum of moving parts, with low inertia and is shock resistant.

In the modification shown in Figure 6 the groove it is replaced by a helical rib 30 on the spindle and the blades 12, are arranged to grip the rib with a tongue and groove engagement which restricts backlash. As in the previous example the width of the blades is substantially parallel to the helix at the position of engagement and the movement of the blades is substantially perpendicular to the helix.

As is well known the frictional resistance to rotation of a spindle such as that described above is dependent, among other factors, on the diameter of the pivots and it is usual practice to make this diameter as small as is possible consistent with strength in order to reduce the friction. Figures 7 and 8 illustrate an arrangement which permits a further reduction in frictional resistance to be effected. The solid spindle employed in the previous construction is replaced by a tube 40 which is provided at its ends with jewel bearings 41. The tube is supported on a fixed wire 42 which is held under tension between the plates 43, 44 of the instrument frame. The Wire, being under tension, may be made of less diameter than the pivots formed on the ends of the spindle as in the previous construction and will have adequate strength to support the spindle.

The invention may be applied to instruments for indicating characteristics other than pressure. For example the stop may be operable by a bi-rnetallic heat responsive strip or by expansion of a metallic rod for temperature measurement or by direct mechanical force (e. g. in a dial test indicator) or by electro-magnetic force. A heat responsive bi-metallic strip may be employed for indicating electrical characteristics. For instance to measure volts the strip may be surrounded by a heating coil of resistance wire to which the voltage is applied and to measure amperes the current may be passed through the material of the strip itself to heat the strip by its own resistance. The strip may in this last arrangement be divided by a longitudinal slit extending from its fixed end nearly to its free end (the stop end) and the current caused to flow from one portion of the fixed end to the stop end and back along the other portion to the fixed end.

It is within the invention to operate the pointer spindle directly by means of a bi-rnetallic or other responsive strip. Thus for example the free end of a bi-metallic heat responsive strip or of a pressure responsive tube may be engaged directly in a helical groove in the operating spindle, in this case no stop as described above being required. This arrangement is suitable for use where it is not essential for the instrument to be shock-resistant.

I claim:

1. In a guage including condition responsive means movable to positions proportional to the value of a condition, indicator means movable to indicate said value, and a translating means adapted to translate movement of said first means into movement of said indicator means, in which said translating means comprises a resilient blade fixed at one end and arranged to have its other end deflected along a path perpendicular to the plane of the blade by'the condition responsive means, said blade being resiliently biased in one direction along its path of deflection, the said other end of the blade having an edge portion lying transverse to the path of deflection, a rotatable pivot shaft arranged to move said indicating means when it rotates, a steep angled helical abutment on said shaft running coaxially with the pivot axis, said straight edge portion contacting said abutment and running parallel to said abutment at the area of contact, and said abutment running perpendicular to the path of movement of said straight edge portion, whereby deflection of said blade by said condition responsive means causes said pivot shaft to rotate and move said indicator to positions indicative of the value of said condition.

2. In a gauge, a translating means as claimed in claim 1 wherein the condition responsive means engages the blade intermediate the length of the blade so that the resilience of the blade tends to reduce the transmission to the pivot shaft of shocks derived from movement of the condition responsive means.

3. In a gauge, a translating means as claimed in claim 1 wherein two parallel spaced-apart helical abutments are provided on the pivot shaft running coaxial ly with the pivot axis, and an antibacklash blade is secured to the blade for movement therewith, said antibacklash blade engaging one of said abutments and the blade engaging the other abutment, said antibacklash blade being resiliently biased with respect to the blade so that the blade and antibacklash blade oppositely engage the abutments under resilient pressure thereby preventing backlash.

4. In a gauge, a translating means as claimed in claim 1 wherein said blade is biased to rotate the pivot shaft, two spaced-apart helical abutments are provided on the pivot shaft running coaxially with the pivot axis, an antibacklash blade is secured to the blade for movement therewith, said antibacklash blade engaging the abutment and being resiliently biased in a direction opposite from the blade so that the blade and antibacklash blades engage opposite edges of the abutment under resilient pressure thereby preventing backlash, said antibacklash blade being of substantially less resilience than the blade and exerting a lesser pressure on the spindle.

5. In a gauge, a translating means as claimed in claim 1 wherein the helical abutment is a side of a helical groove.

6. In a gauge, a translating means as claimed in claim 1 wherein the helical abutment of the shaft is a side of a groove in the shaft, an antibacklash blade secured to the blade for movement therewith, said antibacldash blade engaging the opposite side of the groove and being resiliently biased in a direction opposite from the blade so that the blade and antibacldash blade engage the two opposite sides of the groove under resilient pressure thereby preventing backlash.

7. In a gauge, a translating means as claimed in claim 1 wherein the helical abutment is a side of a rib extending above the surface of the pivot shaft.

8. In a gauge, a translating means as claimed in claim 1 wherein the abutment is a side of a helical rib extending above the surface of the pivot shaft, and an antibacklash blade is secured to the blade for movement therewith, said antibacklash blade engaging the side of the rib opposite the blade and being resiliently biased in a direction opposite from the bias of the blade so that the blade and antibacklash blades engage the opposite side of the rib under resilient pressure thereby preventing backlash.

9. In a gauge including condition responsive means movable to positions proportional to the value of a condition, indicator means movable to indicate said value, and a translating means adapted to translate movement of said first means into movement of said first means into movement of said indicator means, in which said translating means comprises a resilient blade fixed at one end and arranged to have its other end deflected along a path perpendicular to the plane of the blade by the condition responsive means, said blade being resiliently biased in one direction along its path of deflection, said condition responsive means being independent of the blade and acting on the blade against the blade bias, an edge portion on said blade lying transverse to the path of deflection,

a rotatable pivot shaft arranged to move said indicating means when it rotates, a steep angled helical abutment on said shaft running coaxially with the pivot axis, said straight edge portion contacting said abutment and running parallel to said abutment at the area of contact, and said abutment running perpendicular to the path of movement of said straight edge portion, whereby deflection of said blade by said condition responsive means causes said pivot shaft to rotate and move said indicator to positions indicative of the value of said condition.

References Cited in the file of this patent UNITED STATES PATENTS '6 Stanley et al. Oct. 2, Pratt June 9, Hartmann Sept. 19, Buechmann Sept. 1, Dewan June 12, Weingart Dec. 24, Wallace Nov. 18,

FOREIGN PATENTS France Dec. 10, France Dec. 30, Italy Aug. 29, France June 3, 

